/*
 * Fast QR Code generator library
 *
 * Copyright (c) Project Nayuki. (MIT License)
 * https://www.nayuki.io/page/fast-qr-code-generator-library
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 * - The above copyright notice and this permission notice shall be included in
 *   all copies or substantial portions of the Software.
 * - The Software is provided "as is", without warranty of any kind, express or
 *   implied, including but not limited to the warranties of merchantability,
 *   fitness for a particular purpose and noninfringement. In no event shall the
 *   authors or copyright holders be liable for any claim, damages or other
 *   liability, whether in an action of contract, tort or otherwise, arising from,
 *   out of or in connection with the Software or the use or other dealings in the
 *   Software.
 */

package com.ajaxjs.qr_code.fast;

import com.ajaxjs.qr_code.Mode;

import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;


/**
 * A segment of character/binary/control data in a QR Code symbol.
 * Instances of this class are immutable.
 * <p>The mid-level way to create a segment is to take the payload data and call a
 * static factory function such as {@link QrSegmentFast#makeNumeric(String)}. The low-level
 * way to create a segment is to custom-make the bit buffer and call the {@link
 * QrSegmentFast#QrSegmentFast(Mode, int, int[], int) constructor} with appropriate values.</p>
 * <p>This segment class imposes no length restrictions, but QR Codes have restrictions.
 * Even in the most favorable conditions, a QR Code can only hold 7089 characters of data.
 * Any segment longer than this is meaningless for the purpose of generating QR Codes.
 * This class can represent kanji mode segments, but provides no help in encoding them
 * - see {@link QrSegmentAdvancedFast} for full kanji support.</p>
 */
public final class QrSegmentFast {
    /**
     * Returns a segment representing the specified binary data
     * encoded in byte mode. All input byte arrays are acceptable.
     * <p>Any text string can be converted to UTF-8 bytes ({@code
     * s.getBytes(StandardCharsets.UTF_8)}) and encoded as a byte mode segment.</p>
     *
     * @param data the binary data (not {@code null})
     * @return a segment (not {@code null}) containing the data
     * @throws NullPointerException if the array is {@code null}
     */
    public static QrSegmentFast makeBytes(byte[] data) {
        Objects.requireNonNull(data);
        if (data.length * 8L > Integer.MAX_VALUE)
            throw new IllegalArgumentException("Data too long");
        int[] bits = new int[(data.length + 3) / 4];
        for (int i = 0; i < data.length; i++)
            bits[i >>> 2] |= (data[i] & 0xFF) << (~i << 3);

        return new QrSegmentFast(Mode.BYTE, data.length, bits, data.length * 8);
    }

    /**
     * Returns a segment representing the specified string of decimal digits encoded in numeric mode.
     *
     * @param digits the text (not {@code null}), with only digits from 0 to 9 allowed
     * @return a segment (not {@code null}) containing the text
     * @throws NullPointerException     if the string is {@code null}
     * @throws IllegalArgumentException if the string contains non-digit characters
     */
    public static QrSegmentFast makeNumeric(String digits) {
        Objects.requireNonNull(digits);
        BitBuffer bb = new BitBuffer();
        int accumData = 0;
        int accumCount = 0;

        for (int i = 0; i < digits.length(); i++) {
            char c = digits.charAt(i);
            if (c < '0' || c > '9')
                throw new IllegalArgumentException("String contains non-numeric characters");
            accumData = accumData * 10 + (c - '0');
            accumCount++;
            if (accumCount == 3) {
                bb.appendBits(accumData, 10);
                accumData = 0;
                accumCount = 0;
            }
        }

        if (accumCount > 0)  // 1 or 2 digits remaining
            bb.appendBits(accumData, accumCount * 3 + 1);

        return new QrSegmentFast(Mode.NUMERIC, digits.length(), bb.data, bb.bitLength);
    }

    /**
     * Returns a segment representing the specified text string encoded in alphanumeric mode.
     * The characters allowed are: 0 to 9, A to Z (uppercase only), space,
     * dollar, percent, asterisk, plus, hyphen, period, slash, colon.
     *
     * @param text the text (not {@code null}), with only certain characters allowed
     * @return a segment (not {@code null}) containing the text
     * @throws NullPointerException     if the string is {@code null}
     * @throws IllegalArgumentException if the string contains non-encodable characters
     */
    public static QrSegmentFast makeAlphanumeric(String text) {
        Objects.requireNonNull(text);
        BitBuffer bb = new BitBuffer();
        int accumData = 0;
        int accumCount = 0;
        for (int i = 0; i < text.length(); i++) {
            char c = text.charAt(i);
            if (c >= ALPHANUMERIC_MAP.length || ALPHANUMERIC_MAP[c] == -1)
                throw new IllegalArgumentException("String contains unencodable characters in alphanumeric mode");
            accumData = accumData * 45 + ALPHANUMERIC_MAP[c];
            accumCount++;
            if (accumCount == 2) {
                bb.appendBits(accumData, 11);
                accumData = 0;
                accumCount = 0;
            }
        }
        if (accumCount > 0)  // 1 character remaining
            bb.appendBits(accumData, 6);

        return new QrSegmentFast(Mode.ALPHANUMERIC, text.length(), bb.data, bb.bitLength);
    }

    /**
     * Returns a list of zero or more segments to represent the specified Unicode text string.
     * The result may use various segment modes and switch modes to optimize the length of the bit stream.
     *
     * @param text the text to be encoded, which can be any Unicode string
     * @return a new mutable list (not {@code null}) of segments (not {@code null}) containing the text
     * @throws NullPointerException if the text is {@code null}
     */
    public static List<QrSegmentFast> makeSegments(String text) {
        Objects.requireNonNull(text);

        // Select the most efficient segment encoding automatically
        List<QrSegmentFast> result = new ArrayList<>();
        if (text.equals("")) ;  // Leave result empty
        else if (isNumeric(text))
            result.add(makeNumeric(text));
        else if (isAlphanumeric(text))
            result.add(makeAlphanumeric(text));
        else
            result.add(makeBytes(text.getBytes(StandardCharsets.UTF_8)));
        return result;
    }

    /**
     * Returns a segment representing an Extended Channel Interpretation
     * (ECI) designator with the specified assignment value.
     *
     * @param assignVal the ECI assignment number (see the AIM ECI specification)
     * @return a segment (not {@code null}) containing the data
     * @throws IllegalArgumentException if the value is outside the range [0, 10<sup>6</sup>)
     */
    public static QrSegmentFast makeEci(int assignVal) {
        BitBuffer bb = new BitBuffer();
        if (assignVal < 0)
            throw new IllegalArgumentException("ECI assignment value out of range");
        else if (assignVal < (1 << 7))
            bb.appendBits(assignVal, 8);
        else if (assignVal < (1 << 14)) {
            bb.appendBits(2, 2);
            bb.appendBits(assignVal, 14);
        } else if (assignVal < 1_000_000) {
            bb.appendBits(6, 3);
            bb.appendBits(assignVal, 21);
        } else
            throw new IllegalArgumentException("ECI assignment value out of range");
        return new QrSegmentFast(Mode.ECI, 0, bb.data, bb.bitLength);
    }

    /**
     * Tests whether the specified string can be encoded as a segment in numeric mode.
     * A string is encodable iff each character is in the range 0 to 9.
     *
     * @param text the string to test for encodability (not {@code null})
     * @return {@code true} iff each character is in the range 0 to 9.
     * @throws NullPointerException if the string is {@code null}
     * @see #makeNumeric(String)
     */
    public static boolean isNumeric(String text) {
        for (int i = 0; i < text.length(); i++) {
            char c = text.charAt(i);
            if (c < '0' || c > '9')
                return false;
        }
        return true;
    }

    /**
     * Tests whether the specified string can be encoded as a segment in alphanumeric mode.
     * A string is encodable iff each character is in the following set: 0 to 9, A to Z
     * (uppercase only), space, dollar, percent, asterisk, plus, hyphen, period, slash, colon.
     *
     * @param text the string to test for encodability (not {@code null})
     * @return {@code true} iff each character is in the alphanumeric mode character set
     * @throws NullPointerException if the string is {@code null}
     * @see #makeAlphanumeric(String)
     */
    public static boolean isAlphanumeric(String text) {
        for (int i = 0; i < text.length(); i++) {
            char c = text.charAt(i);
            if (c >= ALPHANUMERIC_MAP.length || ALPHANUMERIC_MAP[c] == -1)
                return false;
        }

        return true;
    }

    /**
     * The mode indicator of this segment. Not {@code null}.
     */
    public final Mode mode;

    /**
     * The length of this segment's unencoded data. Measured in characters for
     * numeric/alphanumeric/kanji mode, bytes for byte mode, and 0 for ECI mode.
     * Always zero or positive. Not the same as the data's bit length.
     */
    public final int numChars;

    // The data bits of this segment. Not null.
    final int[] data;

    // Requires 0 <= bitLength <= data.length * 32.
    final int bitLength;

    /**
     * Constructs a QR Code segment with the specified attributes and data.
     * The character count (numCh) must agree with the mode and the bit buffer length,
     * but the constraint isn't checked. The specified bit buffer is cloned and stored.
     *
     * @param md     the mode (not {@code null})
     * @param numCh  the data length in characters or bytes, which is non-negative
     * @param data   the data bits (not {@code null})
     * @param bitLen the number of valid prefix bits in the data array
     * @throws NullPointerException     if the mode or data is {@code null}
     * @throws IllegalArgumentException if the character count is negative
     */
    public QrSegmentFast(Mode md, int numCh, int[] data, int bitLen) {
        mode = Objects.requireNonNull(md);
        this.data = Objects.requireNonNull(data);
        if (numCh < 0 || bitLen < 0 || bitLen > data.length * 32L)
            throw new IllegalArgumentException("Invalid value");
        numChars = numCh;
        bitLength = bitLen;
    }

    // Calculates the number of bits needed to encode the given segments at the given version.
    // Returns a non-negative number if successful. Otherwise returns -1 if a segment has too
    // many characters to fit its length field, or the total bits exceeds Integer.MAX_VALUE.
    static int getTotalBits(List<QrSegmentFast> segs, int version) {
        Objects.requireNonNull(segs);
        long result = 0;

        for (QrSegmentFast seg : segs) {
            Objects.requireNonNull(seg);
            int ccbits = seg.mode.numCharCountBits(version);
            if (seg.numChars >= (1 << ccbits))
                return -1;  // The segment's length doesn't fit the field's bit width
            result += 4L + ccbits + seg.bitLength;
            if (result > Integer.MAX_VALUE)
                return -1;  // The sum will overflow an int type
        }
        return (int) result;
    }

    static final int[] ALPHANUMERIC_MAP;

    static {
        final String ALPHANUMERIC_CHARSET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:";
        int maxCh = -1;

        for (int i = 0; i < ALPHANUMERIC_CHARSET.length(); i++)
            maxCh = Math.max(ALPHANUMERIC_CHARSET.charAt(i), maxCh);

        ALPHANUMERIC_MAP = new int[maxCh + 1];
        Arrays.fill(ALPHANUMERIC_MAP, -1);

        for (int i = 0; i < ALPHANUMERIC_CHARSET.length(); i++)
            ALPHANUMERIC_MAP[ALPHANUMERIC_CHARSET.charAt(i)] = i;
    }
}
